Control apparatus



United States Patent .8 232 i I 2o (I, I use .y, l

" It I 5.9

Primz zry Examiner- Robert G. Nilson Attorneys-Arthur H. Swanson, Lockwood D. Burton and G. Donald WeberJr.

ABSTRACT: An apparatus to provide direct and reverse 7 proportional control as well as direct and reverse differential gap with or without reset and rate action by employing a hollow block shaped casing to accommodate the insertion of different interchangeable process variable, set point, and negative feedback modules through the sides of the casing that have springs on their inner ends for eliminating any undesired difference in the gradient of these modules and for introducing forces in different angular directions to the free end of a rockable post member located at the center of the block and wherein a flapper that is spring biased for moving contact against the post member and a nozzle supplying a regulatable fluid pressure against the flapper is mounted for rotatable movement with a proportional band adjusting disc to different individual positions that will provide any selected one of the aforementioned four types of control.

Patented Aug. 18, 1970 Sheet i of 6 1 PM! M INVENTOR. WILLIAM W. BASSETT gLwggwmx AGENT.

Patented Aug. 18, 1970 3,524,462

s heet 1- of 6 RATE RESET DIRECT PROPORTIONAL REVERSE PROPORTIONAL F l G. 6

INPUT SET POINT ADJUSTMENT DIRECT REVERSE DIFFERENTIAL GAP DIFFERENTIAL GAP FEEDBACK 304 284 I 58? R ME I. 302 u 7 I '1 Nu I MANUAL RESET o I sET POINT SPAN T RESET (REP/MIN) v -32O mun" l llllllllll'll "will BIG 3 3|6 INVENTOR.

WILLIAM W; BASSETT AGENT;

Pat ented Aug. 18,1970

sheet 6 of 6 IIHHHHIHIHIIH Ohm INVENTOR. WILLIAM w. BASSETT Patented Aug. 18, 1970' I 3,524,462

INVENTOR. WlLLlAM W; BASSETT' AGENT. v

CONTROL APPARATUS It is an object of the present invention to provide a flapper actuator in the form of a rockable post member having a selected one of a number of pair of opposing spring force applying responsive means connected thereto to apply forces of different magnitude to this post member to thereby position the flapper with respect to a nozzle associated with this flapper and to alter the control pressure generated in the nozzle.

More specifically it is another object of the present invention to provide a block for the body of a controller having apertures therein to accommodate the insertion of any one of a number of different types of responsive units therein such as a bourdon, a rolling diaphragm and piston and a manually adjusted means to apply different magnitudes of forces to an end of separate springs associated with these responsive units so that the springs may in turn apply a resultant motion to the aforementioned flapper actuator that is proportional to the magnitude of the collected forces being applied by the responsive units.

It is another object of the invention to provide a rotatable disc for altering the position of the flapper to different angular positions on the rockable post member so that the motion transmitting effect that selected ones of the responsive units have on the positioning of the flapper is increased while the motion transmitting effect that other remaining responsive units have on the position of the flapper are decreased.

It is another object of the invention to provide a rotatable disc for rotating the nozzle and flapper mounted thereon to different angular positions so that a shifting between direct and reverse acting proportional and differential gap control can take place without requiring the operator to reverse the fluid pressure connections attached to the element under control such as a valve in a flow line.

It is another object of the invention to alternatively attach the aforementioned bourdon, rolling diaphragm and piston and other actuating means to a spring so that a force that is proportional to a process variable can be applied to the aforementioned flapper actuator and to attach a rolling diaphragm or a manually adjustable force applying means to a spring so that a force proportional to a set point can be applied to the aforementioned flapper actuator.

' It is another object of the present invention to provide an adjustable gradient compensating cantilever spring between one of the aforementioned springs and the rockable flapper actuating post member which will eliminate the tedious past practice of being required to select only precisely matched responsive units for this control apparatus that have the same gradient characteristics.

A better understanding of the present invention may be had from the following detailed description when read in connection with the accompanying drawings in which:

' FIG. 1 shows an exploded view of a flapper nozzle unit and a flapper actuating post member and how different magnitudes of forces can be applied by way of responsive units and springs to move the member and flapper in relation to the nozzle;

FIG. 2 is a plan view ofFIG. 1;

FIG. 3 shows how responsive means in the form of rolling diaphragm capsules and gradient compensating means can be employed in place of the responsive means and gradient compensating means shown in FIG. 1;

FIG. 4 shows a side elevation view of the gradient compensating means shown in FIGS. 1 and 3;

FIG. 5 is a plan view of how the flapper and nozzle unit as shown in FIG. 1 can be mounted in a hollow block for rotation with a proportional band adjusting disc;

FIG. 6 is a schematic view showing how the flapper and nozzle of FIG. I and FIG. 5 which are mounted for rotation on a disc can be rotated with the disc from their solid line direct proportional control gradient position to a reverse proportional, reverse differential gap and direct differential gap quadrant dotted line positions about the flapper actuating post member;

FIG. 7 is a plan view of the block shown in FIG. 5 with a top plate mounted thereon to retain the proportional disc on the casing and;

FIG. 8 shows a bottom view of FIG. 7 and how a selected one of several types of responsive units can be used as modules for mounting in the hollow block casing to move the springs and the rockable post and flapper shown in FIGS. 1, 5, and 6 in lieu of the casing shown in FIG. 2;

FIG. 9 is the opposite side of a modular casing disclosed in FIG. 8 and also shows a view that is similar to FIG. 5 but with the modular parts associated with the block shown in FIGS. 5 and 7 removed;

FIG. 10 is a view taken along the lines 10-10 of FIG. 5 to show a typical view of how the modules as shown in FIGS. 5 and 8 are inserted in the hollow block shown in the latter mentioned figures.

The control apparatus 10 shown in FIGS. 1 and 2 is supported within a casing 12 having an adjustable plate 14 in a manner similar to that disclosed in the Horst R. Thieme Pat. No. 3,349,787.

The stationary end portion 16 of a responsive means for example a bourdon tube 18 is mounted on the plate 14 and the free end of this bourdon tube is pivotally connected to one end ofa coil spring 20.

A second responsive means 21 is employed to adjust the set point of the control apparatus 10. This set point adjusting means 21 is comprised of a plate member 22 having a wall 24 forming a slot therein and two connecting screws 26, 28 to fixedly attach one ofits ends to a stationary member 30.

A pin 32 is shown in FIGURE l fixedly mounted in one position within the confines of the wall 24 forming the slot in the plate number 22 by means of a pair of washers at 32, 34 and a screw member 36 that is threadedly mounted in the other end of the pin 32.

The inner end of the pin is shown having a conical shaped end portion 38 for bringing it into point contact with the spring plate member 40. This spring plate member 40 is fixedly connected at one end to a stationary member 42 by means of two threaded screw connections 44, 46. The other end of the plate member 40 has a wall 48 forming an aperture therein to receive one end of the second coil spring 50.

It can be seen from FIG. 1 that the loosening of screw 36 and the manual movement of the pin 32 to the right of 'the position shown will reduce the amount of set point adjusting force that is applied to the spring 50 by way of the spring plate 40.

In a similar but opposite manner it can be seen that manual movement of the pin 32 to the left of the position shown in FIG. 1 will increase the set point adjusting force that the spring plate 40 applies to the coil spring 50. This is possible because in this position the inherent resiliency of the spring plate 40 will be allowed to partially return to a position when the pin 32 does not exert quite as great a stress as it can when it is in the position shown in FIG. 1.

A cam 52, a shaft 54, that is mounted on a stationary bearing 56 and an adjustable knob 58 as shown in FIGS. 1 and 2 are supported for rotation in the bearing 56 to move the left end of the plate member 22 towards and away from the plate 40 from the position shown in FIGS. 1 and 2.

A third responsive means may take the form of the negative feedback link portion 60 that is shown mounted for rotation on the adjustable support plate 14.

Feedback motion is transmitted to the link 60 when up or down motion of the stem 62 of the pneumatic valve 64 occurs. The construction of the linkage 65 shown in dotted line form in FIG. 2 which translates the motion of the valve stem 62 in the form of rotary motion to the shaft 66 and the cam support plate 68 is similar to that disclosed in detail in the aforementioned Horst R. Thieme Pat. No. 3,349,787.

The outer peripheral surface of the cam 70 mounted by means of screw 72, 74 on the cam support plate 68 is rotated with the shaft 66 against roller 114 forming one end of the negative feedback link portion 60. This action will in turn rotate the screw shaft 116 mounted on the negative feedback link portion 60 about its pivot bearing 118 and the aforementioned negative feedback motion introduced by the stem will thus be transmitted by way of the ring connection 120 to the coil spring 122.

A fourth responsive means may take the form of the adjustable negative feedback balancing means 124. This balancing means is comprised of a plate 126 having a cylindrical part 128 fixed thereto and protruding outwardly therefrom. The central portion of this cylindrical part 128 is shown in FIG. 1 in engagement with a threaded screw member 130 whose head 132 is in engagement with the stationary plate 134.

A guide pin 136 is shown attached to a stationary member 138 and passing through a wall 140 forming an aperture in plate 126 to guide the plate 126 in a straight back and forth direction without tilting as the screw 132 is rotated in a clockwise and counterclockwise direction. Additional apertured wall portions 142, 144 can also be employed for similar guides.

A lug 146 which forms an integral part of the plate 126 has an apertured wall 148 therein to which one end of the coil spring 150 can be attached for movement therewith.

The inner end of the set point spring 50 and negative feedback spring 122 are shown connected to a circular plate 152 by looping their ends through respectively associated apertured wall portion 154, 156 formed in the circular plate 152.

Similar gradient compensating cantilever leaf spring units 158, I60, 162 of FIGS. 1, 2, and 3 are best shown in detail in FIGS. 3 and 4 as being constructed of a flexure plate 164 pivoted in a cantilever fashion at one end to a stationary member 166 and fixedly supporting the lower end ofa pair of flexible members 168, 170. One of these flexible members 168, is curved towards the flexible member 170 and has an apertured wall 172 formed in an end portion thereof. The other one of the flexible members 170 is curved towards the first mentioned curved flexible member 168 and is shown passing there through for up and down movement in its apertured wall 172.

Each of the gradient compensating leaf spring units 158, 160, 162 also have a sphere 174 mounted between them that is in contact with the edges of a second slotted wall 176 formed in a flexible member 168. One end of the plate 178 is fixedly connected to the sphere 174 and the other end 180 is made of a forked construction for contacting a nonthreaded necked portion 182 of the bolt 184.

A bolt 184 is centrally connected as shown in FIG. 4 to a stationary member 186 for rotatable up and down movement thereon so that the plate 178 and sphere 174 may be raised between the converging sides of the flexure members 168, 170.

lt can thus be seen from the aforementioned description that adjustment of the bolt 184 will introduce changes in gradient into the diametrically opposed springs shown in FIGS. 1 3 to compensate for any undesired differences in gradient inherent in any two diametrically opposed responsive means such as may be present in the bourdon 18 and the set point adjusting means 21 as shown in FIG. 1 or which may exist between the rolling diaphragm capsule units on 88 and 190. Each of the cantilever spring units 158, 160, 162 will thus eliminate the need for selecting only responsive means that have identical spring gradients as has herebefore been the practice.

The adjustable cantilever spring unit 158 is shown connected at one of its ends in any suitable manner for movement with the inner end of the coil spring and is connected at another one ofits ends for movement with the coil spring 192.

The adjustable cantilever spring unit 160 is shown connected at one ofits ends in any suitable manner for movement with the inner end of spring 150 and is connected at another one of its ends for movement with the coil spring 194. The inner end of the coil spring 192 and coil spring 194 is shown connected to the circular plate 152 by looping the ends of these springs 192, 194 through their respective associated apertured wall portions 196, 198.

The circular plate 152 and the embossed portion 200 fixed thereto form an integral part of the post 202 and therefore move in unison with this post.

A bottom portion 204 of the post 202 is of a cone shaped configuration and is mounted on a cone shaped bearing 206 formed in casing 12 for rocking of a longitudinal axis of the post 202 thereon.

The rotatable post 202 has a first ring shaped plate 208 fixedly connected to the post 202 adjacent the pivoted end of the post 202. A second ring shaped plate 210 that is spaced from the first ring shaped plate 208 is shown retained in a fixed position on the casing 12 by means of a suitable number of screw connections 212, 214.

A conical shaped spring 216 is shown extending between the second stationary ring shaped plate 210 having a circular spring retaining portion 218 and the first ring shape plate 208 to apply a force to the plate 208 and the cone shaped end 204 of the post 202 in order to retain it in point contact with its associated bearing 206.

FIG. 1 and FIG. 5 discloses the upper end of the rockable post 202 as having a ring shaped shoulder 220 thereon. When the flapper 222, 224 and nozzle 240 of FIG. 1 is assembled over the shoulder 220 of rockable post 202 the portion 222 will be retained in physical contact with the ring shaped shoulder 220.

The flapper portion 222 is fixedly connected by a suitable bonding material to the other portion of the flapper 224 which in turn is made of a resilient material.

The resilient flapper portion 224 in turn is mounted by means of a screw 226, a support plate 228 and spacer 230 on a lug 232 formed in a dished out portion 234 of a manually rotatable proportional band adjusting disc member 236 shown in FIG. 5, rather than on an invertable cup shaped member 237 shown in FIG. 2.

A second screw 238 is employed to retain the end of the nozzle support plate 228 and a nozzle 240 supported thereon in fixed relation with a second lug 242.

The tip of the nozzle 240 is initially positioned in spaced relationship with the resiliently supported flapper 222, 224 and a regulatable filtered air supply under pressure, not shown, which is transmitted by way of flexible conduit 243 to and out of the nozzle 240 in the direction of the arrow shown on FIG. 1 against the flapper portion 224.

The changes in pressure that take place within the nozzle are amplified in a well known manner by means of a pilot valve 243 and then employed to apply pressure by way of conduit 244 to a control element for example the head of the pneumatic control valve 64 shown in FIG. 2.

Each of the previously mentioned rolling diaphragm capsule units 188, 190 are constructed of an associated stationary cup shaped casing 246; 248 having a circular bulbous ring shaped portion 250; 252 formed integral with the base of their respective casings 246; 248. The ring portion 250 retains an entire open cylindrical end portion of a rolling diaphragm number 254 in pressed fit engagement against the inner wall of the casing 246. The ring portion 252 likewise is used to retain the open end of the rolling diaphragm number 256 and pressed fit engagement against the wall of its casing 248.

The respective closed ends of the rolling diaphragm 254, 256 have flat surfaces bonded for joint movement with their respective pistons 258; 260.

One end of a flexible wire member 262 is connected in any suitable manner to the center of the piston and its other end is shown connected by means of a ring 264 to the upper end of the flexible member of the gradient compensated leaf spring unit 162. A spring 266 extends in partially compressed relation between the piston 258 and a stationary part 268 to apply a spring force to the piston 258 and the right portion of the rolling diaphragm 254 as the process variable (P.V.) pressure applied by way of the conduit 270 to the interior of the rolling diaphragm capsule 188 is increased.

When this increase in applied pressure occurs the flexible wire member 262 the gradient compensating 162 and spring 192 is moved to the right of the position shown in FIGURE 3.

If a decrease in the process variable (P.V.) pressure then occurs, this reduction in pressure allows the spring 266 to move the piston 258 rolling diaphragm 254, flexible wire 262, the gradient compensating unit 162, and the left end of the spring 192 in a direction back to their original position.

A spring 272 extends in partially compressed relation between the piston 260 and the stationary part 274 to apply a spring force to the piston 260, the right end of the spring 50 and the left portion of the rolling diaphragm 256 when an increase in set point pressure is applied by a pressure regulator, not shown, through the right end of the conduit 276 to the interior of the rolling diaphragm capsule unit 190.

If a decrease in the regulated set point (S.P.) pressure then occurs this reduction in pressure will allow the spring 266 to move the piston 260, rolling diaphragm 256, and the right end of spring 50in a direction back to their original positions.

When the process variable and set point pressures are equal, the force that each of these units shown in FIGS. l and 3 will apply to the post will be equal and directly opposite to one another and the post 202 will then return the flapper portions 222, 224 in a fixed spaced relationship with the nozzle 240.

FIGURE 6 schematically shows the position that the proportional band adjusting disc member 236 and the nozzle 240 and flapper portions 222 and 224 will be in as the disc member is rotated from a solid line nozzle flapper position in which direct proportional control is effected to their other dotted line positions in which the reverse proportional, reverse differential gap and direct differential gap type of controller can be affected.

More specifically it can be seen that the proportional band adjusting disc 236 shown in FIG. 5 has been rotated to a position in which the numeral twenty on the reverse differential gap quadrant scale that extends from numeral one to eight clockwise has been placed opposite the index marked 278 on the hollow block casing 280.

In FIGURES 5 and 6 it can be seen that the scales for the different types of quadrants extend between the numerals 1 1and s.

It can also be seen by observing FIGURES l and 5 that the rockable post 202 will be pulled in a direction to allow the resiliently mounted flapper to be flexed by its inherent spring characteristics away from the nozzle when the process variable pressure within the bourdon 18 is increased beyond the force exerted by the set point adjusting unit 21.

It can further be seen that as the proportional band disc 236 is rotated to other positions, the force which it allows to be applied to move the flapper parts 222, 224 by means of the rockable post 202 can be varied from a nonaffective force value where it merely allows the post to dissipate its force by moving it along the length of the flapper part 222 without adjusting the flapper parts toward or away from the nozzle to a position where substantially all the force applied by the bourdon 18 that exceeds the force applied by the set point unit 21 will be used to directly alter the position of the post 202 and flapper portions 202, 224 with respect to its associated nozzle 240 and thereby alter the control pressure therein.

The internal portions of the hollow block casing 280 shown in FIGS. 5, 7, 8, 9 and 10 are constructed similar to the part 12 to accommodate the mounting of the post 202 its associated spring parts 20, 158, 192, 150, 160, I94, 50, 122 and its associated flapper portions 224, 222, and nozzle 240 which are shown in assembled position in FIGURE 5.

FIGURE 7 shows a view similar to FIGURE 5 but with a plate 282 mounted on the casing 280 by means of screw connections 284, 286, 288. It can be seen that the plate 282 retains the proportional band disc 236 in a circular dished out portion 290 of the casing 280. This plate 282 also has a punched in portion 291 protruding from its underside surface which is constructed to engage a stop member formed on the upper surface of the dished out member 234 to prevent continuous angular rotation of the disc 236 beyond the limit where all of its scale indications can be readily aligned with the index 278.

A wall 292 forming the lower left corner of the plate 282 shown in FIGURE 7 is purposely cut away to allow manual finger proportional band adjustment of the knurled edge 294 formed on the periphery of the proportional band disc 236.

A wall 296 is shown in the plate 282 to form a cut away portion to enable the operator to observe what mode of control scale and what setting on this scale he is aligning with the triangular proportional band index marking 298 as shown in FIGURE 7 that is formed. on the plate 282.

Other walls 300, 302 as shown in plate 282 and in the hollow block casing 280 form cut away portion into which a rotatably mounted manually rotated reset knob 304 is inserted.

Other walls 306, 308 as shown in the plate 282 and in the casing 280 are employed to form cut away portions into which a knurled manually rotated set point adjusting knob 310 is inserted. The knob 310 is rotated by manually turning its outer top knurled portion until a desired set point setting is aligned with the triangular index marking 312.

Other walls 314, 316 as shown in the plate 282 and in a removable reset valve block 317 forming a part of the casing 280 provide cut away portions into which a knurled rotatably mounted manually located reset adjusting knob 318 is inserted.

The knob 318 is rotated by turning its outer top knurled portion to a desired reset setting that is aligned with the triangular index marking 320. As shown in FIGURE 5 the aforementioned removable reset valve block 317 and a rate adjusting valve block 322 each have a lip 324; 326 protruding therefrom through which a pair of screw connections 328, 330; 332, 334 extend and which are threadedly engaged with associated threaded wall portions 336, 338; 340, 342 in the block 280 shown in FIGURE 9.

The reset valve 317 and the rate valve 322 each have a manually adjusted screw actuated valve 344; 346 associated with passageways having fluid passing therethrough, not shown, to allow reset and rate action to be individually or jointly introduced or eliminated from the pneumatic control circuit by rotating these parts 344, 346 so that they are moved in an outward or inward direction with respect to the block 280. The screw adjusting valve 346 is employed for adjustment to a position in which the rate adjusted valve 348 will be bypassed and the screw adjusted valve 344 is employed for adjustment to a position in which the reset adjusted valve 334 will be cut out of the line carrying the flow of the fluid as positive feedback fluid pressure when operating under a reverse differential gap position of the disc 236, rod shoulder 220, nozzle 240 as shown in FIGURE 5 or when these parts are mounted as a unit in a direct differential gap scale position that is aligned with the index 278.

The rate valve 322 also has a manually adjustable knob 348 which is adjusted in the same manner as the previously described adjusting knob 318.

Reset and rate circuitry, not shown, which is associated with the reset valve 322 and rate valve 317 is constructed and operated with the adjustable pneumatic negative feedback units 372 and 304 in substantially the same manner as the reset and rate circuitry which is disclosed for the controlling apparatus of the Robert Schmidt Patent Application Serial No. 403,228, now Patent No. 3,379,205. It should be understood that since the embodiment shown in FIGURE l employs a mechanically operated lever 60 to apply negative feedback by way of spring 122 and circular plate 152 to the post 202 and since the means 124 employed to adjust the level of the negative balancing force is mechanical this FIGURE 1 embodiment is therefore not adapted to have reset or a rate valve action incorporated therein.

Neither for the same aforementioned reason can either of the mechanically adjusted modules 369, 370 employ either the aforementioned reset valves 322 or rate valve 317. When reset or rate valve unit mode of control is used it should be noted that pressure actuated capsules such as capsules 188, 190,372 or 304 shown in FIGS. 3 and 8 are employed in place of the mechanical feedback lever 60 and its associated level adjusting unit 124 shown in FIG. 1.

From the aforementioned description it can be seen that the casing 280 shown in FIGS. 5, 7, 8, 9, and 10 is provided with internal hollowed out wall portions to accommodate the mounting of the rockable post 202 and the four spring units extending therefrom as shown in FIGURE 1. It can also be seen that a conventional pressure connection 350 can be employed to transmit an input process variable pressure P.V. from an external source, not shown, through the wall of the casing 12, the tubing 352 to the bourdon 18 or alternately through the conduit 270 to the diaphragm capsule unit 188.

The movable end of the bourdon 18 to which springs shown in FIGURE l are attached extends through the outer end of wall 354 forming an aperture in the block 280. An alternate module 188 containing the FIGURE 3 type of diaphragm capsule, and springs as that shown in FIGURE 1 can be mounted within the wall 354 forming aperture in the block 280.

Another alternate third module 356 can be assembled in the wall 354 forming the aperture in the block casing 280. This module 356 has a rotatable cup shape member 358 threadedly engaged for transverse movement along the adjustable screw member 360 which in turn is retained by means of a spring 362 fixedly attached thereto against rotation in suitably located notches 364, 366 formed in portion of the wall 354 near the left side of the block shaped casing 280.

The right end of the screw 360 has an eyelet 368 fixed thereto through which the left end of the spring 20 is attached for transverse movement with the screw 360 when the cup member 358 is rotated in either a clockwise or counterclockwise direction.

The other manual reset adjusted knob 369, the set point adjusting knob 310 and the rate adjusting knob 370 are all constructed of substantially the same modular construction as thatjust described for the module part 356.

FIGURE 8 shows how alternate fluid pressure actuating modules 372, 190, 304 can be substituted for the manually operated modules 369, 310 and 370.

Each of the oppositely positioned pressure actuated units 304, 372 are similar in construction and function in the manner as the diametrically opposed module pressure units 188 and 190 shown in detail in FIGURE 3 when the respective fluid pressures representing reset and rate action are applied as negative feedback pressure by way of the flexible tubings 374, 376 from the previously described reset and rate valves 317, 322. More details of these reset and rate circuits are described in the aforementioned Robert Schmidt patent application Serial Number 403,228, If only a negative feedback fluid pressure from a rate valve unit 322 per se is applied by way of tube 374 to module 372 the knob 369, its associated spring 122 and module 304 are not used.

If only negative feedback fluid pressure from the reset valve unit 322 per se is applied by way of tube 376 to module 304 the knob 370, its associated spring 50 and its module 372 are not used.

As the aforementioned manually actuated modules 356, 369, 310, 370 or the pressure actuated pressure models 188 or 18; 372, 190; 304 or any combination of these manual and pressure actuated modules apply varying magnitudes of forces to their associated springs for example 20, 150, 50 and 122 the resultant motion that will be applied to the rockable post 202, by way of the disc 224 mounted thereon, will cause the post to be rocked with the flapper 224 in a direction toward or away from the nozzle 240 depending in which direction the resultant forces of the springs are acting on the post 202. When the direction of the flapper moves toward or away from the nozzle 240 this will respectively increase and decrease the control pressure being produced within the nozzle.

It can be seen that the direction of the process variable (P.V.) Set Point, (S.P.) feedback and reset rate forces acting on the springs 264 or 20; 122, 50, 150 are always in the same direction.

It can also be seen that the disc 236 containing the flapper nozzle 224, 240 can be moved to the quadrant of the disc identified as differential gap in FIGS. 6 and 7 opposite the indicator 298, as shown in FIGURE 7. When this is done the effect of an increase in the process variable P.V. will cause the post 202 to move along the flapper 224 as long as this process variable (PV) remains below the value of the preselected Set Point rather than against the flapper 224 and the flapper 224 will remain in a substantially closed position against the nozzle. The new relationship which the flapper 222 takes with respect to the rockable post 202 will, as previously described, cause a positive feedback pressure to be applied in the aforementioned manner by way of the springs to the post 202 as long as e.g. the level ofa fluid being supplied to a tank by way of a control valve 64 is below an upper Set Point (S.P.) tank level value. This will thus hold the control pressure in the nozzle 240 at its highest level until the desired Set Point (S.P.) tank level is reached. As this action occurs pressure is applied to the head of a control member such as an pneumatically operated valve 64 by way of the pilot valve 243 and conduit 244 to cause a batch control operation such as controlling the level of the fluid in a tank only when the level exceeds or goes below any one of a series of preselected values. This will take place by fully opening the valve 64 in the conduit 244 only after the level of the tank drops below a predetermined low level. When the liquid flowing into the tank has reached a preselected upper level and the magnitude of the Process Variable (P.V.) exceeds the magnitude of the Set Point value it can be seen that the flapper 224 will be forced by the spring forces acting on the post 202 into a fully opened non-restrictive nozzle position and the control pressure then acting on the control valve 64 will be held at a preselected low pressure level. When this takes place the lower fluid pressure then being applied to the head of the valve 64 will close the valve 64 and no further control action will again take place until the level in the tank again drops below the preselected low level.

The batch control action just described is thus the differential gap action that can be achieved when any one of the proportional differential gap proportional band settings on the disc 236 are aligned with the index 298 as shown in FIGURE 7. It should be understood that direct differential gap" means that increases in the nozzle pressure will result in increases in pressure being applied to the head of a reverse acting control valve 64 to move the stem and plug thereof to an open position. lt also means that decreases in the fluid pressure in the nozzle 240 will result in the opposite effect, namely, the lowering of the fluid pressure being applied to the control valve which will enable the spring 378 of the valve to move the stem 62 and plug 380 thereof to a fully closed position.

When the disc 236 is moved to any index indication on the reverse differential gap quadrant scale then any increase in the pressure in the nozzle 240 will result in a decrease in the magnitude of the fluid pressure acting on the control valve 64 and vice versa.

lClaim:

l. A control apparatus, comprising a member operably connected for rocking movement at one end on a stationary support, a first and second responsive means to apply opposing spring forces to opposite sides of the member each in accordance with the magnitude of a different variable to move the longitudinal axis of the member toward and away from a substantially perpendicular position with respect to its stationary support, a rotatable member positioned in spaced apart relationship with the rockable member, a flapper flexibly connected to the rotatable member for movement therewith, a nozzle fixedly positioned on the rotatable member adjacent the flapper, a conduit to transm t a preselected fluid pressure to and through the nozzle against the flapper, the flexible connection of the flapper being operable to maintain the flapper in physical spring biased contact with the rockable member for movement therewith to thereby effect a change in the magnitude of a control fluid pressure generated in the nozzle as differences in the magnitude of the variables takes place and a biasing means positioned about the rocking member and extending between a fixed plate and an end portion of the rocking member adjacent the stationary support is employed to maintain the longitudinal axis of the member in a substantially perpendicular position on the stationary support.

2. The control apparatus as defined in Claim 1 wherein the first responsive means for applying a spring force to the rockable member is varied in accordance with the magnitude of a process variable pressure and the magnitude of the spring force applied by the second responsive means to the rockable member is varied in accordance with the magnitude of a preselected set point pressure.

3. The control apparatus as defined in Claim 1 wherein the first responsive means is a bourdon that is actuated by a process variable pressure and the second means is a rolling diaphragm and piston unit that is actuated by a set point pressure.

4. The control apparatus as defined in Claim 1 wherein the first responsive means is a rolling diaphragm capsule that is actuated by a process variable pressure and the second means is a rolling diaphragm and piston unit that is actuated by a set point pressure.

5. The control apparatus as defined in Claim 1 wherein the first responsive means is a bourdon that is actuated by a process variable pressure and the second means is a manually adjusted spring unit.

6. The control apparatus as defined in Claim 1 wherein the changes in the magnitude of the control fluid pressure is applied to actuate a control element, a first characterized spring member attached at one end to another side of the rotatable member, the control signal is connected for application to a rate valve to convert it into a delayed fluid pressure negative feedback rate signal, a first rolling diaphragm capsule having its diaphragm connected for movement with the other end of the first spring, a conduit for applying said fluid pressure rate signal to the diaphragm in the rolling diaphragm capsule, a second characterized spring member attached at one end to a side of the rockable member at a position that is opposite that of said first spring member, the control signal is connected for application to a reset valve to convert it into a positive fluid pressure feedback reset signal, a second rolling diaphragm capsule having its diaphragm connected for movement with the other end of the second spring, and a conduit for applying said fluid pressure reset signal to the diaphragm and the rolling diaphragm capsule.

7. The control apparatus as defined in Claim 1 wherein the fluid control pressure in the nozzle is operably connected by way of a conduit to move a control element, a third responsive means is employed to apply a negative feedback spring force to another side of the rockable member in accordance with the magnitude of the control fluid pressure and wherein an adjustable spring force is applied to a side of the rockable member that is opposite to the side on which the negative feedback force is applied to thereby provide a negative feedback level adjustment for said third responsive means, the manual rotation of the rotatable member in one direction being operable to move the flapper through different angles while it moves along a peripheral surface of the rockable member to a direct acting position in which position an increase occurring in the magnitude of the process variable pressure will effect a movement of the flapper toward the nozzle and cause an increase in the control fluid pressure in the nozzle to occur and wherein manual rotation of the rotatable member in an opposite direction will move the flapper to a selected reverse acting angularly displaced position on the outer surface of the rockable member in which latter mentioned position an increase occurring in the magnitude of the process variable pressure will effect a decrease in the magnitude of the control fluid pressure in the nozzle.

8. The control apparatus as defined in Claim 1 wherein the first responsive means for applying a spring force to the rockable member is varied in accordance with the magnitude of a process variable pressure and the magnitude of the spring force applied by the second means to the rockable member is varied in accordance with the magnitude of a preselected set point pressure, and wherein additional oppositely positioned pairs of responsive means that respectively respond to changes in negative feedback pressure and a negative feedback level adjustment are connected to apply rocking movement to the rockable member, and wherein rotation of the rotatable member in one direction is operable to move the flapper to a differential gap proportional band position wherein an increase in the force supplied above a preselected value by the process variable will affect movement of the rockable member along the flapper and maintain the flapper in a substantially closed position against the nozzle to thereby effect an immediate rise in the control pressure therein for use in a batch control operation and the responsive means collectively being additionally effective to immediately allow the resilient portion of the flapper to be moved by the rockable member to a fully open non restricted position away from the nozzle when the control pressure has reached a preselected high control pressure level.

9. A control apparatus, comprising a member operably connected for rocking movement at one end on a stationary support, a first and second responsive means to apply opposing spring forces to opposite sides of the member each in accordance with the magnitude of a different variable to move the longitudinal axis of the member toward and away from a substantially perpendicular position with respect to its stationary support, a rotatable member positioned in spaced apart relationship with the rockable member, a flapper flexibly connected to the rotatable member for movement therewith, a nozzle fixedly positioned on the rotatable member adjacent the flapper, a conduit to transmit a preselected fluid pressure to and through the nozzle against the flapper, the flexible connection of the flapper being operable to maintain the flapper in physical spring biased contact with the rockable member for movement therewith to thereby effect a change in the magnitude of a control fluid pressure generated in the nozzle as differences in the magnitude of the variables take place and wherein the first and second responsive means has spring members in series connecting it to the rockable member and wherein one of the springs is of a cantilever configuration to compensate for any undesired differences in spring gradient that is present between the first responsive means and the second means. 

